I have two types of Yarrow (Achillea millefolium). One is a hand me down and the other is named 'Paprika.' I've let them grow together. It is interesting to me how the colors seem to clash if they are separate, but once they are grown together, complement each other. There is nothing black and white about color! btw- I came up with that phrase myself! :)
My Red Hot Pokers (Kniphofia uvaria), really put on a show this year. I have them planted in front of my Cannas bed. I like how the dark leaves set them off. If you haven't seen 'The Queen' with Helen Mirren, check it out. There is a scene with a row of Kniphofia that is breathtaking!